English

intermonthly

From inter- + monthly.

Proto-Indo-European *h₁én ‘in’

Proto-Indo-European *h₁entér ‘between’

Proto-Italic *n̥ter ‘between’

Latin inter ‘between’

Middle English *monethly ‘monthly’

Today it means

adj Between months

Language periods are conventional ranges, not dates for this word.

Etymograph / intermonthly